The title of A Field in England is a completely accurate description of the film's setting, from beginning to end. Which makes it all the more impressive that it feels like a lengthy journey, even when the surroundings stay more or less the same.

By design, the sense of place is largely static throughout. The same tall grass (the better to hide within during a moment of terror). Surrounded by the same trees. Underneath the same bright white cloudy sky. And director Ben Wheatley shoots it all in crisp black-and-white, in key moments using the high contrast to frame his characters as small, dark shadows inside wide, bright compositions.

There's very little else to place them in any particular time or place. But for the costumes and the vernacular, this could be taking place anytime. And but for the title, it could be taking place anywhere. Yes, we know its official setting is the 17th Century in the midst of the English Civil War, but that's merely a background detail. Even the war itself is kept out of sight - we hear the gun blasts and the chaos, but never catch a good look at the battle. Until finally, the firing stops, and we're left only with that empty field, and we suddenly feel very, very far away from anything tangible or civilized.

Those sidelined on the periphery of the battle are the ones with which we will spend the next 90 minutes - de-facto deserters who walk away from the fight under the pretense of walking to the next town to grab a few pints of ale. If their fellow troops happen to be gone by the time they get back, hey, it's not their fault. All they wanted was a beer.

But what follows does not lead them to any pub - or to much satisfaction at all, for that matter. Rather, the trek transforms into a hallucinatory existential struggle. The key figure is Whitehead (Reece Shearsmith), the personal assistant of an aging alchemist. He has abandoned his post in fear of retribution for not fulfilling his obligation to find a man who stole from Whitehead's master.

He hesitantly joins up with three soldiers, Jacob (Peter Ferdinando), Cutler (Ryan Pope) and Friend (Richard Glover) - the latter of whom at first appears to be dead (Jacob even uses his supposed corpse as a resting spot) but suddenly pops up at the mention of an ale house.

There's a striking sense of gallows humor throughout the proceedings, even as the quartet's journey gets more hellish and disorienting. There is a scene in which one character painfully, agonizingly tries to take a dump - his screams suggest he's not successful - followed by one of his cohorts asking, "Is it a boy or a girl?" Or another scene where one character examines - with a microscope, up close and personal - another's swollen scrotum, and proceeds to casually, exhaustively diagnose him with a whole series of ailments, not the least of which is venereal disease. The man, however, is relieved, because at least he isn't - as he suspected - being turned into a frog by a magical spell.

That last bit of paranoia comes courtesy of O'Neill (Michael Smiley, in a great performance seething with menace and contemptuous arrogance), an Irish alchemist the four deserters discover in the field along their way and who is inclined to make threats about casting insidious spells and such. As it turns out, O'Neill is just the man Whitehead was tasked with finding, and finally he and his new friends are able to capture him, with the intention of taking him back to his master.

O'Neill, however, has other plans, and quickly takes control over the group, and forces them to find treasure he believes is buried somewhere in the field. The three soldiers are all under the influence of hallucinogenic mushrooms, so they're easy enough to control. As for Whitehead - who abstained from the mushrooms so is in full control of his faculties - he's actually easier to control. Unlike the others, he is naïve and cowardly; while they are soldiers who were knee-deep in the ongoing war, Whitehead spent virtually all of his time indoors, his book-learning not doing him much good in the face of actual uncertainty and danger. In a scene that underscores that cowardice (and O'Neill's malevolence), O'Neill invites Whitehead into his tent and either rapes or otherwise tortures and humiliates him - certain visual and dialogue cues strongly suggest the former - to the point where his echoing screams border on a surreal nightmare.

But there's a sense of farce to the power dynamics at play here, which is precisely the point. The film is at times an astonishing visual and sonic experience - consider the extended, violent, grotesque and dreamlike sequence featuring a strobe-like montage of repeated and composite images; or the periodic moments where the characters seem to pose in place, as if for a painting - but it's also a sardonic philosophical comment on the nature of class and subservience. When O'Neill is first captured by the group - before we understand his plans - he takes several moments to get his appearance in order. The film views his vanity as an outright absurdity, only for his pretenses to be justified once he quickly and easily assumes control over the others.

As the absurdities and horrors pile up and the psychological balance among the characters shifts, the film - written and co-edited by Wheatley's frequent collaborator Amy Jump - begins to take on an apocalyptic and metaphysical feel. Whitehead warns of suspecting an imminent danger; the others continually hallucinate a dark cloud directly in their field of vision, rapidly masking the afternoon sky and everything underneath it.

A Field in England is boldly graphic and idiosyncratic, and makes for a captivating - if also frustrating - mixture of black comedy and metaphysical horror, owing to the likes of Ken Russell and Luis Buñuel, among others. I wasn't entirely positive what to make of it at times, but if nothing else, it remains a wholly memorable - and often incredibly funny - experience.